Process for temporarily reducing the crimp index in bicomponent acrylic fibers

ABSTRACT

AN IMPROVED PROCESS FOR PRODUCING HELICALLY CRIMPTED ACRYLIC BICOMPONENT FIBER, WHICH TEMPORARILY REDUCES THE CRIMP INDEX OF THE FIBER COMPRISING; HEATING THE MOIST FIBER UNDER CRITICAL TEMPERATURE, TIME, AND TENSION CONDITIONS IN SUCH A MANNER THAT THE ORIGINAL CRIMP INDEX IS SUBSTANTIALLY RECOVERABLY BY A SUBSEQUENT BOIL-OFF.

United States Patent 3,633,676 PROCESS FOR TEMPORARILY REDUCING THE CRIMP INDEX IN BICOMPONENT ACRYLIC FIBERS Arthur Lulay, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del. N0 Drawing. Filed Jan. 24, 1968, Ser. No. 700,021 Int. Cl. D01d 5/22 US. Cl. 264-468 4 Claims ABSTRACT OF THE DISCLOSURE An improved process for producing helically crimped acrylic bicomponent fiber, which temporarily reduces the crimp index of the fiber comprising: heating the moist fiber under critical temperature, time, and tension conditions in such a manner that the original crimp index is substantially recoverable by a subsequent boil-off.

SPECIFICATION This invention is concerned with improved processes for bicomponent acrylic fiber which provides a temporary adjustment in crimp characteristics to that necessary for good textile processability. Original crimp characteristics are restored by a subsequent relaxed heat treatment.

BACKGROUND OF INVENTION In textile processing of tow and staple an optimum degree of fiber-to-fiber interaction is conducive to elficient operations and best yarn quality. Major deviations from this optimum in either direction result in significant processing difficulties and uneven yarns. The major factor in fiber-to-fiber interaction during textile processing is the character of crimp in the fiber, which may either be introduced by mechanical means or result from a tendency of the fiber to spontaneous development of helical crimp. It is well known in the art to mechanically crimp synthetic fiber at some stage of manufacture prior to textile processing into yarns. Crimp imparted in this manner can be adjusted to that desired for best processability of the tower staple. Such a process for crimp-character adjustment is suitable for either the ordinary single-component synthetic fibers or for those bicomponent fibers which have little or no helical crimp as produced. Bicomponent fiber in which helical crimp develops during manufacture may possess a crimp intensity, as dictated by characteristics desired in the fabrics to be produced therefrom, which leads to excessive sliver cohesiveness, neps, uncommercial loss of fiber due to breakage, and non-commercial yarn evenness. A means to temporarily reduce the helical crimp intensity of precrimped bicomponent fibers would be highly desirable.

SUMMARY OF INVENTION In a process for producing helically crimped acrylic bicomponent fiber which is extruded, extracted, and dried at elevated temperatures in continuous filamentary form during which drying the bicomponent fiber develops helical crimp, the improvement, which temporarily reduces the crimp index of said fiber, comprising: heating the fiber, in a moist condition, to a temperature in the range of about 95 C. to 105 C. for about 0.5 to 2.5 seconds while maintaining the fiber under an elongating load of from about 2 to mg./den., with the proviso that the product of the elongating load and exposure time be in the range of about 2 to about 20 mg.-sec./ den. The fiber may be moist from a previous processing step, e. g., dyeing, or may be moistened by contact with steam prior to, or simultaneously with, the heating as previously described. The described treatment has the effect of temporarily reducing the crimp index of the fiber to a level consistent with good textile processability. The original crimp index is substantially recovered by a subsequent boil-off.

The fiber may be heated by a variety of methods e.g., contact with steam, or heated by contact with internally heated rolls. It is important that heating means heat the fiber surface to within the above-stated range, within the above-stated time range. For this reason, particular methods of heating (e. g. heated dry air) are less suitable because of their lower heat-transfer efiiciency.

It is necessary that the fiber be moist, although no particular water content is essential. If the fiber is treated when taken from a tow dyeing operation, even after scouring and centrifuging to remove most of the water, there is still sufiicient moisture for the purposes of this invention. If the tow is treated immediately after it is produced and dried, or as taken from a package of previously produced tow, sutficient moisture must be supplied, preferably by contacting the fiber with steam. Since the fiber must be heated to a temperature of between about to C., saturated steam at this temperature provides both the required heat and moisture. Saturated steam within the aforesaid temperature range is preferred, although superheated steam may be used if the filaments are previously moistened. Due to the high heat capacity of saturated steam, the fiber is rapidly heated to essentially the temperature of the steam, in addition to being moistened by steam condensation.

The tow must be maintained under an elongating load of about 2 to 20 mg./den. for about 0.5 to 2.5 seconds with the further proviso that the product of the elongating load and exposure time be in the range of about 2 to about 20 mg.-sec./den. Each of these variables must be within the stated ranges to achieve the object of this invention. A lower value in any respect results in inadequate reduction of fiber-to-fiber interactions during textile processing. A higher value in any respect leads to excessive loss in crimp frequency, inadequate fiber-tofiber interaction for good processability and excessive fiber fall-out in the pin-drafting steps.

Definitions and standards Intrinsic viscosity [1 is measured at 25 C. in dimethylformamide, containing 4% by weight of lithium bromide, as the solvent.

Acrylic, as used herein, includes any long chain synthetic polymer composed of acrylonitrile units of the formula iCH C BEL in the polymer chain. As is well understood, the term includes the homopolymer of acrylonitrile (i.e. polyacrylonitrile) and copolymers of acrylonitrile and one or more monoethylenically unsaturated monomers copolymerizable with acrylonitrile.

Although the invention is illustrated in the following examples in terms of a single bicomponent acrylic fiber composition, it is not so limited. It is applicable to any acrylic bicomponent fiber which develops most of its helical crimp potential on drying under conditions such as described. Such bicomponent fibers are exemplified by those prepared from two polymeric components selected from the group consisting of polyacrylonitrile; copolymers consisting essentially of at least about 88% by weight acrylonitrile and up to 12% by weight of at least one member of the group consisting of addition monomers which are non-ionizing in neutral media and addition monomers bearing sulfonate groups; and mixtures of two or more of said polymers, said polymeric components having no more than 90 meq./ kg. of combined anionic function, the two components being present in the cross-section in a weight ratio in the range of 75/25 to 25/75, said components differing by at least 1% by weight in copolymerized monomer.

Among the addition monomers useful in this invention as exemplary of those which are non-ionizing in neutral media are methyl acrylate, methyl methacrylate, vinyl acetate, styrene, methacrylamide, methacrylonitrile, vinyl chloride, vinylidene chloride, methyl vinyl ketone and the like as well as any of the available vinyl pyridines. The latter class of comonomers is of special interest; under neutral conditions such copolymerized compounds act as neutral modifiers, while during exposure of the fiber to a pH below about 3 they act as bases, providing a useful degree of acid-dyeability. The preferred compounds include methyl acrylate, vinyl acetate, styrene and the vinyl pyridines.

Among the copolymerizable sulfonates are the sulfonated styrenes, vinyl sulfonate, allyl sulfonate, methallyl sulfonate and their alkali-metal or alkaline-earth metal salts, and the like, it being necessary only that the compound chosen from this class be copolymerizable with acrylom'trile to the desired extent. The preferred compounds are the sulfonated styrenes.

Bicomponent fiber, as used herein, includes composite fiber which contains two components in a side-by-side relationship in the cross section of the fiber and extending substantially throughout the length of the fiber, so that each constitutes a portion of the fiber surface. Fiber includes both continuousand staple-length structures; filament" is specific to continuous length structures unless otherwise specified. These bicomponent fibers are characterized by their tendency to develop helical crimp, which in some cases is present in the fiber as produced, or may be developed by subsequent treatment at high temperature. Reversals in the direction of helices may occur frequently in the fibers.

Combined anionic function is determined on the polymers by the following procedure:

A l-inch diameter tube equipped with a stop-cock at the lower end and having a total capacity of 500 ml. is charged successively with 200 ml. of dehydrated Amberlite IR-l H resin and 200 ml. of Amberlite MB-3 resin so that the MB-3 resin is in the upper part of the column. Both of these resins are available from the Rohm and Haas Chemical Company in a water-wet form. [The IR-120 H resin is a strongly acidic sulfonated polystyrene type resin with exchange capacity of at least 1.7 milliequivalents of cations per milliliter (4.6 milliequivalents per gram). The MB-3 resin is a mono-bed exchange resin comprising equivalent amounts of IR-12O H and Amberlite IRA-410 in the fully regenerated form. Total capacity is at least 0.5 milliequivalent per milliliter. IRA-410 is a strongly basic quaternary ammonium polystyrene type resin.] They are dehydrated by slurrying in a flooded bath with dry acetone until no further shrinkage of the resin bed occurs. The acetone is then displaced by dry, deionized dimethylformamide (DMF). The resin is stored under dimethylformamide (DMF) until used in the analysis.

To a 2.5-gram sample of polymer in 250 ml. of dry deionized DMF is added a small amount of a pH indicator comprising equal parts of 0.01% alcoholic solutions of Neutral Red and Xylene Cyanol FF indicators. The polymer solution is passed through the prepared resin column at a rate of about 10 ml. per minute. The resin bath is kept covered by liquid during this procedure, deionized DMF being used at the end to displace the last of the sample. The indicator serves to distinguish the acidic polymer solution from the pure DMF at both the beginning and the end of the sample emergence from the column.

A portion of the deionized polymer solution, in which the polymer now exists in the free acid form, is evaporated to dryness to determine solids content. Another portion is then titrated with standardized alcoholic potassium hydroxide to determine acidity, the added indicator now showing the titration end point. A simple calculation which compares this result with a blank experiment, wherein pure DMF replaces the polymer solution, establishes the meq./kg. of acidity in the polymer sample. Neither component should have a combined anionic function of more than meq./kg., and preferably the combined anionic function of each component should be in the range of about 25 to 70 meq./ kg.

Helical crimp frequency, F, and crimp index, CI, are measured on an extended length basis. One 360 convolution is counted as one crimp, whether in Z or S configuration. The extended fiber length in which the crimps are counted is then measured and the number of crimps per unit length calculated. To measure the length of a staple fiber, it is smoothed out on a granduated surface. At least 5 fibers selected at random are measured, and an average value of F determined. CI is a measure of the percent of apparent fiber shortening due to the crimp configuration. The fiber length, L,., is determined by loading a single fiber of from about 3-6 denier with 5 mg. A second length determination L, is made under a load of 150 mg., which serves to remove all the crimp without extending the fiber. Crimp index is calculated as follows:

Coefiicient of variation, CV, is a measure of unevenness of a fibrous structure such as a sliver or a yarn. It is conveniently obtained by use of the Uster evenness tester Model B equipped with a quadratic integrator, using the manufacturers procedure for the measurements. The higher value of CV, the poorer the yarn (or sliver) evenness.

Lea product is a measure of the comparative breaking load of a skein of yarn adjusted for the linear density of the yarn. It is calculated as the product obtained by multiplying the breaking load (expressed in pounds) of the skein by its linear density expressed in cotton count (the number of 840 yd. hanks per 1b.).

To measure elongating load, the tow is threaded past a set of adjustable tensioning bars and through the heated space. A simple spring scale is attached to the tow and the force required to move it at a rate of 6 yds./min. (about 5.5 m./min.) is noted. The tensioning bars are adjustable to require a greater or lesser wrap angle until the desired restraint is attained. It is necessary that the measurement of elongating load be made under the conditions to be employed in the operation of this invention. Differing resistance to passage over the tensioning bars and differing restraints on the tow at the source may otherwise lead to major deviations from the desired value.

Measurement of static and dynamic cohesion Static. An approximately IO-inch (25.4-cm.) length of sliver of about 230 grams/yd. (about 147,000 den.) and composed of fibers having a maximum length less than 10 inches (25.4 cm.) is elongated in an Instron at the rate of 100% per minute. Cohesion, in mg./den., is defined as the maximum strain observed.

Dynamic. A sliver of about 230 grains/yd. (about 147,000 den.) in which all fibers have a length of less than about 7 inches (about 18.7 cm.) is processed between pairs of rolls at a draft of 9.7, using a 7-inch (about 18.7 cm.) distance between the rolls. The front, or drafting, rolls are rotated at a surface speed of 21.2 yds./ min. (19.4 m./min.); they are retained at the specified spacing by attachment to a load cell. The strain developed by drafting is reported in terms of g./ den. based on the denier of the drafted sliver.

EXAMPLES The invention is further illustrated by the following examples which are not to be construed as limitative. In the examples, parts are by weight unless otherwise specified.

Example I This example illustrates the preparation of continuous bicomponent filamentary tow suitable for processing by the improved process of this invention. Subsequent examples illustrate the processing of samples of filamentary tow of this example and filamentary tow similar thereto, according to this invention.

Bicomponent acrylic fiber is spun from two solutions of the following compositions: Component A is produced from a 31.5% solution in dimethyl formamide (DMF) of a terpolymer of 93.8% acrylonitrile, 6.0% methyl acrylate and 0.2% sodium styrenesulfonate; Component B is produced from a 23.8% solution in DMF of a mixture of 90% polyacrylonitrile and of the terpolymer of component A. The terpolymer has an intrinsic viscosity of 1.5 and a combined anionic funcition of 55.6 meq./kg. The homopolymer has an intrinsic viscosity of 2.0 and a combined anionic function of 27 meq./kg. The solutions are spun as described in the Belck and Siedschlag US. Pat. 3,039,524, using spinnerets in which the two solutions meet at the counterbores and flow side-by-side through the capillaries. The solutions are fed at equal rates such that the weight ratio of polymeric component A to polymeric component B in the fiber is 58/42.

The filaments are spun into a hot, inert gas which flows concurrently therewith through an enclosure and serves to evaporate most of the solvent therefrom before the filaments are withdrawn. Filaments from a number of such spinning positions are accumulated to a tow of about 500,000 denier, comprising filaments of about 6.3 denier per filament exclusive of about 25% solvent based on the total weight.

The tow is passed through a series of water baths controlled at a temperature of 95 C. through which extraction liquor flows counter-currently to the tow path-oftravel. Fresh, hot water is continuously added to the final bath, and an aqueous solution of DMF is removed from the first for recovery of the solvent it contains. During passage through the extraction tanks, the tow is drawn, stepwise, to 193% of its as-spun length and the DMF is reduced to less than 2%, based on fiber weight.

The washed and drawn tow is lightly mechanically crimped in a stufier box crimper of the type described in the Hitt U.S. Pat. 2,311,174 which facilitates handling between crimping and drying.

The tow is distributed uniformly on the perforated belt of a continuous dryer and exposed to air heated to 140 C. for a period of 6.1 minutes and at a temperature of 135 C. for an additional 3.1 minutes. Due to high shrinkage while being dried, the final denier-per-filament is 6. Total denier is approximately 470,000.

Example II This example illustrates this invention wherein dried tow is contacted, under the conditions of this invention, with saturated steam.

A sample of tow is prepared in accordance with the procedure of Example I. The fiber exhibits a helical crimp of 15.2/inch (5.9/cm.) and a crimp index of 13.6. After boiling in water for 30 minutes and drying under no restraint, the fiber exhibits a crimp frequency of 16.9/ inch (6.7/cm.) and a crimp index of 19.0. e

A portion of the tow is passed through a chamber into which steam is fed at such a rate as to maintain an atmosphere of saturated steam at atmospheric pressure, despite the cooling effect of the entering tow, at such a speed as to result in an exposure time of 1.13 seconds while under a restraining tension load of 2.4 milligrams per denier. The tow is then laid down in an open container. The steamed tow is found to have a helical crimp of 15.3/inch (6/cm.) and a crimp index of 2.5. After boiling in water for thirty minutes and drying under no restraint, these values are 15.4 (6.1) and 18.7, respectively.

The steamed tow and an equal quantity of the un- Steamed Unstreamed Fiber from Tow:

Percent 01 (as is) Percent 01 (boiled oft) C.p.i. (cp.cm.) (as is) C.p.i. (cp.cm.) (boiled ofi) 2nd Cpir r draft sliver:

Static cohesion (mg/denier) Dynamic cohesion (g./denier) Fmayarn:

Lea product When processed to knitted fabrics and subjectively evaluated for this use, both items are found to be satisfactory in bulk, tactility and resistance to development of surface distortions when tumbled in a manner approximating the fabric-on-fabric working encountered during actual wear.

Substantial improvement in processing efiiciency is encountered during the processing of the steamed fiber. This is reflected in the lower sliver cohesion (smoother drafting, less fiber breakage, and less loss of short fibers) and in the indicated improved evenness of the yarns. These factors are further delineated in Example III, which follows.

Example III This example further illustrates the embodiment of this invention wherein dried tow is contacted, under the conditions of this invention, with saturated steam. The example also more clearly illustrates the benefit to textile processing of the process of this invention.

Two further quantities of essentially identical tow are prepared in accordance with the procedure of Example I; each is subjected to steam substantially as done in Example II, with two exceptions: (1) in each case the tow is passed directly from the steaming operation to a rotary cutter of the well-known Beria type and (2) the tow forwarding speed is varied at two cycles/ min. between limits which result in a residence time in the steam chamber of 0.95 to 1.2 seconds and a random cut length within the limits of 4 and 5 inches (10.2 and 12.8 cm.). Restraining load is adjusted to 3.6 mg./den. The two lots of stable are designated A and B. A second portion of the tow used to produce Lot A is varicut in the same manner without exposure to the steam. This lot is designated C.

All three lots of stable are processed on the worsted card, five pin draftings, slubbing and spinning to 1/ 13 worsted-count yarns having 7 t.p.i. Z twist. Properties and performance characteristics are summarized in Table 2.

TABLE 2 Lot A Lot B Lot 0 Fiber from tow:

C.I. (as is) 1. 8 1. 1 12. 2 0. 9 15. 3 20. 2 8) 8. 0(3. 3) 14. 0(5. 5) 0) 16. 1 (6. 4) 14. 5(5. 7)

Average inches (cm) 3. 5(8. 9) 4. 28(10. 8) 2. 81 (7. 2) Percent below 2" (5.1 cm.).. 14 1 34 Percent below 2 (6.3 cm.) 20 2 45 Sliver cohesion after second pin drafting:

Static (mgJdenier) 1. 9 3. 2 10. 8 Dynamic (g./denier) 0. 3 0. 36 1. 91 Yarn:

C 14. 4 14. 1 15. 9 Lea product 1, 1,125 966 The steamed items of this test, although borderline in their low as-is crimp frequency, demonstrate clearly the advantages to textile processability of the process of this invention. The longer stable lengths after carding and pin drafting are illustrative of less fiber breakage in processing, which is the result of reduced 'fiber-to-fiber interaction.

Example IV this staple is processed on a worsted card, using a cylinder speed of 260 r.p.m. and a stripper speed of 280 rpm, a weak 'web is formed, and a heavy deposit of fiber is found beneath the stripper roll. The sliver is processed through five stages on pin drafting, slubbing and spinning to 8.73 cotton-count yarn having 7 t.p.i. (2.76 t.p. cm.) Z twist. After second pin drafting, the fiber comprising the sliver is found to have an average length of 4.09 inches (about 10.3 cm.) and 95% of the fiber is found to be below 5.25 inches (13.3 cm.).

The yarn has a Lea product of 12/17 and a CV of 12.0 and is judged to be of excellent quality.

In a control experiment, a second portion of the tow, as previously described in this example, is cut to -inch (12.7-cm.) staple and stock-dyed burgundy using basic dyes and means available in the art. When such fiber is processed on the worsted card under the same conditions as previously described in this example, with a cylinder speed of 280 rpm, and a stripper speed of 300 r.p.m., the web appearance is only fair. An excessive TABLE 3 Crimp characteristics Restraint (mg. pd.) As steamed After boil-01f Time of X time of restraint exposure exposure CF, c.p.i. F, e.p 1 Item (mg. pd.) (seconds) (seconds) 0.1. (cp. cm.) 0.1. (cp. em

3.6 0.61 2.2 4.0 16.5 (6.5) 15.6 14.8 (5.8) 3.6 1.51 5.45 3.1 18.4 (7.3) 15.5 17.0 (6.7) 3.6 2.43 8.75 2.9 18.2 (7. 2) 13.1 16.1 (6.4) 16.3 0.61 9.95 3.0 10.3 (4.1) 15.4 14.4 (5.7) 16.3 1.51 24.6 0.8 7.0 (2.8) 14.1 15.1 (6.0) 6 16.3 2.43 39.5 1.0 5.3 (2.1) 15.2 13.3 (5.2) Untreated 10.6 17.0 (6.7) 14.6 15.8 (6.2)

Items 1 through 4 are found to have superior processability and to lead to yarns of improved evenness. Items 5 and 6 exhibit borderline processability and confer somewhat inferior bulk in knitted fabrics prepared therefrom.

It is seen that a range of restraints from about 2 to about 20 mg./den. and a range of exposures from 0.5 to 2.5 seconds are satisfactory for the process of this invention if the product of restraint in mg./denier and exposure in seconds is in the range of 2 to 20 mg.-sec./den.

Example V The example illustrates this invention wherein moist tow, after it is removed from a dye bath, is contacted with internally heated rolls under the conditions of this invention.

A sample of tow is prepared in accordance with procedure of Example I. The tow has a crimp frequency in the range of 14 to 22 per inch (about 5.5 to 8.6 per cm.) and a crimp index in the range of to 16.

A portion of the tow is dyed black using basic dyes and means available in the art. It is scoured and centrifuged to remove most of the water. The nearly dry tow (about to 50 percent of water by weight) is threaded over several stationary guides, which serve to arrange the filaments in a uniform lateral distribution, and passed over a series of rolls heated internally to 116 C. at such a rate as to dry the tow completely, but not heat the tow above 105 C. The speed is adjusted to provide a substantial amount of crimp elimination as estimated by appearance of the emerging tow. The exposure time and restraining tension are adjusted to temporarily reduce the crimp index of the fiber. A sample of the tow,

when boiled for minutes in water, has a crimp index of 15.0 and a crimp frequency of 20.2/inch (8/cm.).

The dyed tow is processed on a Pacific Converter to 4.5- inch (11.4-cm.) varicut staple. The staple has an average length of 4.39 inches (about 11.1 cm.); 95% of the fiber is below 5.3 inches (about 13.4 cm.). When amount of fiber is observed to fall to the floor below the stripper, and an additional large amount of short fiber is observed to have deposited on and near the card. Card sliver weight is 200 grains/yd. (about 127,000 den.). Fiber from the sliver is found to have an average length of 1.63 inches, and 95% of the fibers are below 3.1 inches, indicating a nonacceptable degree of fiber breakage during carding. The sliver is not processed further.

The above comparison illustrates the improvement provided by the present invention, in processes essentially identical in other respects.

Since obvious departures may be made from the conditions employed and the composition used in the description of this invention without departing from the spirit and scope thereof, it is intended that the invention be limited only by the claims which follow.

What is claimed is:

1. In a process for producing helically crimped acrylic bicomponent filaments wherein helical crimp is developed during drying, the improvement which temporarily reduces the crimp index of said helically crimped filaments comprising subsequently heating the filaments while moist to a temperature in the range of 95105 C. for about 0.5-2.5 seconds while maintaining such filaments under an elongating load of from about 220 milligrams/ denier, with the proviso that the product of the elongating strain and exposure time be in the range of about 2-20 milligram-seconds/ denier.

2. Process of claim 1 wherein each of the polymeric components of said bicomponent fibers are selected from the group consisting of polyacrylonitrile; copolymers consisting essentially of up to 1 2% by weight of at least one member of the group consisting of addition monomers which are non-ionizing in neutral media and addition monomers bearing sulfonate groups; and mixtures of two or more of said polymers, said polymeric components having no more than 90 meq./kg. of combined anionic function, the two components being present in the cross-section in a weight ratio in the range of /25 to 25/75, said components differing by at least 1% by weight in copolymerized monomer.

3. Process of claim 2 wherein the said filaments, prior to said heating, are essentially dry and the said heating of said filaments comprises contacting the said filaments with steam at a temperature from about 95 to 105 C.

4. Process of claim 2 wherein the said filaments, prior to said heating, are dyed and are in a moist condition.

References Cited UNITED STATES PATENTS 4/1948 Sissom 264Bicomp. Dig. 8/ 1968 Fujita et a1. 264--Bicomp. Dig. 5/1968 Nakagama et a1. 264182X 2/1969 Holfeld 264-168 X 3/1969 Fujita et a1, 264-103 X 4/1969 Ryan 264--168 X 10/ 1969 Matsui et a1. 264l7l 1/1970 Nishioka et a1. 1---.-- 264-171 FOREIGN PATENTS Great Britain 264-Bicomp. Filament Great Britain 264Bicomp. Filament Great Britain 264Bicomp. Filament Belgium 26471 Great Britain 264--71 Japan 264Bicomp. Tube Japan 264-Bicomp. Tube JAY H. WOO, Primary Examiner US. Cl. X.R. 

